NEW YORK — Bryce Harper passed more concussion tests late Wednesday afternoon before the Nationals let their young star play two days after his scary collision in Monday’s season opener against the Mets.

Manager Matt Williams said doctors and trainers would be checking Harper multiple times during the course of pregame batting practice and other workouts, and any signs of trouble would trigger them to keep the 21-year-old outfielder from playing the game.

“Part of the protocol today is that he will hit, has some rest, evaluate how he feels,” Williams said prior to batting practice. “He’ll go out for BP, come in and rest, we’ll evaluate again how he feels. Sometimes, concussion-like symptoms manifest themselves 24-to-48 hours after the fact. So we just have to keep monitoring that and make sure that he feels good before he goes back out there.”

After the game, Williams said Harper is now considered fully healthy, with no more concern about the incident.

Harper was struck in the head by New York second baseman Eric Young Jr.’s right leg while breaking up a double play in the second inning. He went down in a heap and remained on the ground for about a minute before staggering to his feet and being helped off by Williams and head trainer Lee Kuntz.

Doctors administered a concussion test right after the incident and cleared Harper to re-take the field for the bottom of the inning. Harper also passed another concussion test after the game, though he did say he had a headache at the time.

Harper reported no problems in the 48 hours that passed between Opening Day and his return to Citi Field on Wednesday.

“No, he said he slept great last night,” Williams said. “As of the time he got here today, he has no issue with nausea or dizziness or anything like that. Part of our protocol is to make sure we monitor his BP today, too. If he has any issues, then we’ll address it.”

Harper went through his pregame drills with no issues, then took the field for warm-ups around 6:50 p.m.

“We rely on the doctors,” Williams said. “I’m not a doctor. Lee certainly has a set of questions that he asks him, and those answers would dictate what he thinks. But we ultimately rely on the doctor. And what kind of tests they administer and their findings after the fact. So that’s what we go by.”